The present invention is generally directed at spraying nozzles and systems for use in aerial sprayers or crop dusters. More specifically, the present invention includes an aerial spraying nozzle for inducing an electrostatic charge upon a sprayed liquid.
Aerial spraying has long been used as a means of applying herbicides, pesticides, fungicides and other forms of treatments to crops in the agriculture, horticulture and forestry industries. Aerial spraying is typically performed by modifying an aircraft to include a liquid reservoir in fluid communication with a plurality of nozzles held in place by one or more booms attached to the aircraft. The spray itself is usually formed by pumping a chemical liquid mixture contained within the reservoir through each nozzle to form a spray cloud of liquid droplets which deposit upon the crop upon flying thereover. It is known that in order to enhance the deposition of these droplets onto the crop, an electrostatic charge can be induced onto the spray upon exiting the nozzle. It is also known that the minimum charge-to-mass ratio needed to be induced on such sprays to observe any appreciable enhancement in deposition is 0.8 millicoulumb/kilogram (mC/kg).
There exist in the art several United States patents which have attempted to address the issue of inducing an electrostatic charge upon a spray during aerially spraying. Such examples include U.S. Pat. Nos. 4,560,107; 5,402,723; and 5,975,425. However, shortcomings in the prior art exist as extremely high voltage outputs are needed to induce a proper charge-to-mass ratio on the resultant electrostatically charged spray, ranging from at least 5 kV to 35 kV. Using such extremely high voltages to induce an electrostatic charge onto the spray has its inherent risks, including the possibility of inducing a high potential onto the aircraft in the event of equipment malfunction which could have deleterious effects, possibly fatal, when the pilot attempts to land. Further, for purposes of efficiency, it is desirable to impart upon the spray the maximum amount of charge per volt applied, which can lead to the employment of larger volumetric capacity aerial spray systems than what are currently being used.
There therefore exists a need in the art to provide an aerial spraying apparatus to achieve these goals, namely the ability to induce an adequate electrostatic charge onto an aerially sprayed liquid at relatively lower voltages than what is currently known, preferably less than 5 kV.